Work on this project concerns the following research on AMV and MC29 tumor virus: (1) study of the early changes in the cell after virus infection, (2) examination of the DNA associated with these two RNA tumor viruses, (3) search for evidence of virus--specified RNA and DNA in cells in culture after infection with virus. The DNA associated with the virus has a sedimentation coefficient of 11 S and is located within the center structure of the virion (nucleoid). RNase treatment causes the DNA to have a lower sedimentation rate. This would suggest that the DNA molecule contains a short strand of RNA. This possibility is being investigated.